[PATCH v10 0/7] Rust Abstractions for PWM subsystem with TH1520 PWM driver

[Uwe Kleine-König]

Hello Michal,

On Thu, Jul 10, 2025 at 03:48:08PM +0200, Michal Wilczynski wrote:
> On 7/10/25 15:10, Uwe Kleine-König wrote:
> > On Thu, Jul 10, 2025 at 10:42:07AM +0200, Michal Wilczynski wrote:
> >> On 7/7/25 11:48, Michal Wilczynski wrote:
> >>> The series is structured as follows:
> >>>  - Expose static function pwmchip_release.
> > 
> > Is this really necessary? I didn't try to understand the requirements
> > yet, but I wonder about that. If you get the pwmchip from
> > __pwmchip_add() the right thing to do to release it is to call
> > pwmchip_remove(). Feels like a layer violation.
> 
> It's required to prevent a memory leak in a specific, critical failure
> scenario. The sequence of events is as follows:
> 
>     pwm::Chip::new() succeeds, allocating both the C struct pwm_chip and
>     the Rust drvdata.
> 
>     pwm::Registration::register() (which calls pwmchip_add()) fails for
>     some reason.

If you called pwmchip_alloc() but not yet pwmchip_add(), the right
function to call for cleanup is pwmchip_put().

>     The ARef<Chip> returned by new() is dropped, its reference count
>     goes to zero, and our custom release_callback is called.
> 
> [...]
> >>> ---
> >>> base-commit: 47753b5a1696283930a78aae79b29371f96f5bca
> > 
> > I have problems applying this series and don't have this base commit in
> > my repo.
> 
> Sorry for the confusion. Base commit doesn't exist in the mainline
> kernel or linux-next, cause I've added some dependecies for compilation,
> like IoMem for the driver (uploaded full branch on github [1]). The
> bindings however doesn't depend on anything that's not in linux-next.

The series didn't apply to my pwm/for-next branch.

Note that the base-commit should always be a publically known commit.
See the chapter about "Base Tree Information" in git-format-patch(1).

Best regards
Uwe
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